A Vuilleumier heat pump (VHP) is a thermodynamic apparatus in which thermal energy from a source, such as a combustor or solar, as well as energy from the environment is extracted to provide heating. The amount of energy available for heating is greater than the amount of fuel energy supplied to the combustor because it is supplemented by the energy from the environment. A VHP can also be used for cooling by extracting the energy from the conditioned air and then dumping excess energy to the environment. A Stirling engine (SE) is a thermodynamic apparatus operating by cyclic compression and expansion of the working fluid at different temperatures, such that there is a net conversion of thermal energy to mechanical work.
Both the VHP and the SE have an energy source (combustor, usually) and a cylinder with one displacer reciprocating with the cylinder in the SE and two displacers in the case of the VHP. VHPs and SEs are closed devices with a working gas at high pressure. The most commonly used working fluids in SEs and VHPs is helium. In many prior art systems, a plurality of tubes that are fluidly coupled to the cylinder extend into the combustion space to effect a transfer of energy from the combustion gases and the working fluid. The brazing of the tubes is a known failure point. With there being so many tubes, ensuring integrity of the system is painstaking. The combination of high pressure and the working gas being a small molecule that passes through materials, even materials such as metals which for most purposes are nonporous, presents challenges. The fewer parts that are coupled together, leak opportunities are reduced. Additionally, it is desirable to integrate several of the apparatuses' components into a single piece for making the device more compact, decreasing weight, decreasing material cost, and decreasing package complexity. Furthermore, it is desirable to supplant the multiple tubes with a more robust architecture.